2997

Modification of physical properties of poly(L-lactic acid) byaddition of methyl-β-cyclodextrinToshiyuki Suzuki1,2, Ayaka Ei2, Yoshihisa Takada2, Hiroki Uehara2, Takeshi Yamanobe*2

and Keiko Takahashi3

Full Research Paper Open Access

Address:1Perkin-Elmer Japan Co. Ltd., 134 Godo-cho, Hodogaya-ku,Yokohama-shi 240-0004, Japan; Fax: +81-45-339-5861, 2GunmaUniversity, 1-5-1 Tenjin-cho, Kiryu-shi, Gunma 376-8515, Japan; Fax:+81-277-30-1331 and 3Tokyo Polytechnic University, 1583 Iiyama,Atsugi 243-0297, Japan; Fax +81-46-242-3000

Email:Toshiyuki Suzuki - toshiyuki.suzuki@perkinelmer.com;Takeshi Yamanobe* - yamanobe@gunma-u.ac.jp; Keiko Takahashi -takahasi@chem.t-kougei.ac.jp

* Corresponding author

Keywords:crystallinity; DSC; methyl-β-cyclodextrin; poly(L-lactic acid); Ramanspectroscopy

Beilstein J. Org. Chem. 2014, 10, 2997–3006.doi:10.3762/bjoc.10.318

Received: 15 July 2014Accepted: 24 November 2014Published: 16 December 2014

This article is part of the Thematic Series "Superstructures withcyclodextrins: Chemistry and applications II".

Guest Editor: G. Wenz

© 2014 Suzuki et al; licensee Beilstein-Institut.License and terms: see end of document.

AbstractPoly(L-lactic acid) (PLLA) is a biodegradable plastic and one of the most famous plastics made from biobased materials. However,

its physical strength is insufficient compared to general-purpose plastics. In this study, the effect of methylcyclodextrin (MeCD)

addition on the structure and physical properties, especially the drawing behavior, of PLLA was investigated. Through thermal

analysis, it was found that MeCD addition lowers the crystallinity and enhances the mobility of PLLA. The sample containing

approximately 17% MeCD was drawn to more than 1000% at 60 °C, although PLLA fractured at a strain of less than 100%. Differ-

ential scanning calorimetry (DSC)-Raman in situ measurements also revealed decreases in the glass transition temperature (Tg),

cold crystallization temperature (Tc), and melting point (Tm), and improvement in structural distribution with temperature. DSC-

Raman measurements simultaneously supplied information about crystallinity and thermal properties. Thus, it was concluded that

MeCD had high affinity for PLLA, and the addition of MeCD increased the amorphous component of PLLA and enhanced the

drawability.

2997

IntroductionPoly(L-lactic acid) (PLLA) has attracted attention because it is a

biodegradable polymer derived from carbon-neutral resources.

However, its melting point (Tm) of approximately 170 °C must

be increased because of the low thermal resistance. The melting

point of the stereo complex (Sc) of PLLA and poly(D-lactic

acid) (PDLA) is higher than 220 °C [1-5], which is comparable

Beilstein J. Org. Chem. 2014, 10, 2997–3006.

2998

Figure 1: Thermo-gravitometry for PLLA, PL-MCD83, PL-MCD67, PL-MCD50 and MeCD.

to that of aromatic polyester. Many studies have been conducted

for improving this thermal property using Sc [6-16].

PLLA is a brittle polymer, but the polymer should have a high

toughness so that it can be used for mechanical purposes.

Tensile drawing is one method of improving mechanical prop-

erties, since it effectively induces molecular orientation [17-27].

However, the brittleness of PLLA prevents drawing. To

improve this, it is necessary to control the interchain interac-

tions and lower the glass transition temperature (Tg) of the

amorphous phase.

Cyclodextrins (CDs) are cyclic molecules composed of six (α),

seven (β), or eight (γ) glucose units. CDs have hydrophobic

cavities that can contain guest molecules and form inclusion

complexes (ICs). ICs with α-CD accelerate the nucleation and

crystallization of poly(ε-caprolactone), poly(ethylene glycol),

poly(butylene succinate), and poly(3-hydroxybutyrate) by

acting as a nucleation agent [28-33].

Several attempts have been made to form ICs between CDs and

PLLA, and their structures and physical properties have also

been analyzed [34-36]. It has been reported that the loss factor

peak, tanδ, shifted to a higher temperature because of IC forma-

tion [37]. In the solid ICs of CDs and PLLA, the CD–CD inter-

actions are dominant over the PLLA–PLLA interactions. There-

fore, by forming an IC, CD increases the Tg of PLLA, which is

not desirable for the improvement of mechanical properties.

Since this results from strong CD–CD interactions, a modified

CD may improve the mechanical properties of PLLA. Methyl-

β-cyclodextrin (MeCD) is soluble in chloroform, as is PLLA,

and the affinity of MeCD for PLLA may be sufficient to

improve the mechanical properties of PLLA.

In order to analyze the interchain interactions of polymers, it is

necessary to acquire information about their thermal properties

and structure. Differential scanning calorimetry (DSC) is a very

useful method for analyzing the thermal properties such as Tg

and cold crystallization temperature (Tc). However, it does not

provide details about the structural change. On the other hand,

Raman spectroscopy reveals the vibrational states of functional

groups, but not thermal properties because irradiation affects

the sample temperature [38]. For exact and expeditious struc-

tural analysis, it is important to determine simultaneously the

thermal properties and the local structure [39,40]. Recently,

DSC and Raman spectroscopy (DSC-Raman), which simultane-

ously measure thermal behavior and Raman vibrational states,

was developed. The purpose of this study is to investigate the

effects of MeCD on the local structure and physical properties

of PLLA by DSC-Raman spectroscopy.

Results and DiscussionThermal propertiesFigure 1 shows the thermogravimetric analysis (TGA) results

for MeCD, PLLA, PL-MCD83, PL-MCD67, and PL-MCD50.

PL-MCD83, PL-MCD67, and PL-MCD50 refer to the mixtures

of MeCD and PLLA with 83, 67, and 50 wt % of PLLA, res-

pectively. Below 200 °C, a weight loss is observed, except for

Beilstein J. Org. Chem. 2014, 10, 2997–3006.

2999

PLLA. For MeCD, this weight loss arises from dehydration

[41,42]. For PL-MCD samples, the weight loss begins at higher

temperatures than for MeCD. The weight loss is caused by

desorption of chloroform from the MeCD cavity. This weight

loss may not be observed if PLLA is included in the MeCD

cavity, indicating that an IC with PLLA is not formed.

The 10% weight loss temperatures for PL-MCD50, 67, and 83

are lower than those of PLLA and MeCD. Since the decomposi-

tion is affected by crystallinity, the mixing of MeCD with

PLLA lowers the thermal resistance because of the increase in

the amorphous phase. In other words, MeCD causes PLLA to

be disordered.

Above 400 °C, most samples decompose, and at 800 °C, less

than 12% of the residues of the decomposed samples remain. At

800 °C, PLLA and MeCD had 2 and 16 wt % of the residue,

respectively. The decomposition weight loss of PLLA and

MeCD mixture can be calculated from the linear relationship

between the pure PLLA and MeCD if the interaction between

MeCD and PLLA does not exist. Figure 2 shows the actual

weight loss caused by decomposition at 800 °C and the theoreti-

cal weight loss line (the solid line). From this figure, it is clear

that the actual weight loss is less than the theoretical weight

loss. This means that the environment around the mixed MeCD

and PLLA samples is different from that of pure PLLA and

MeCD. Since the IC between PLLA and MeCD does not form

according to the above results, the environmental changes

around MeCD and PLLA may be caused by their high misci-

bility in each other. Therefore, MeCD acts as a plasticizer for

PLLA. The plasticizing effects of triacetin and oligomeric

poly(1,3-butylene glycol adipate) on PLLA have been reported

[43-46]. Although these plasticizers are reported to be superior

to MeCD, MeCD is a biobased material and is thus advanta-

geous from an environmental perspective.

These TGA results show that MeCD acts as a plasticizer for

PLLA, and the fraction of the amorphous phase increases. Since

the Tg of the samples may be affected by the MeCD addition,

DSC measurements were also carried out. Figure 3 shows the

DSC curves. For PLLA, the Tg and endothermal peak of

melting are observed at approximately 70 and 180 °C, respect-

ively. In addition, a slight cold crystallization is observed at

approximately 120 °C [15,47-49]. Addition of MeCD alters the

DSC curves. For PL-MCD83 and 67, Tg decreases to approxi-

mately 60 °C; similar trends were observed for Tc and Tm. For

PL-MCD50, Tg and Tc are higher than those of PL-MCD67 and

83, while their Tm is approximately equal. The enthalpies of

fusion for PL-MCD50, 67, and 83 are approximately equal to

the enthalpies of cold crystallization. Therefore, the melting of

PL-MCD50, 67, and 83 are caused by the crystals formed

Figure 2: Observed weight loss and stoichiometric line.

through cold crystallization, and it can be concluded that

PL-MCD50, 67, and 83 are amorphous. As the Tg and Tc

decreased, the mobility of the amorphous phase increased

through the addition of MeCD. It has been reported that the

unmodified α-CD accelerates the crystallization of PCL, PEG,

PBS and P3HB during cooling from melts. Cooling measure-

ments by DSC were carried out for PLLA, PL-MCD50, 67 and

83 to confirm the similar effects. However, the crystallization

was not observed for PLLA, PL-MCD50, 67 and 83 with a

cooling rate of 10 °C·min−1. Therefore, MeCD does not have a

potential to accelerate the crystallization of PLLA.

Figure 3: DSC curves for PLLA, PL-MCD83, PL-MCD67 andPL-MCD50.

Tensile drawing behaviorFigure 4 shows the stress-strain curves for the PLLA and

PL-MCD samples at 25, 60, and 100 °C. At 25 °C, all samples

fractured at less than 20% elongation in Figure 4c. The breaking

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Figure 4: Stress-Strain curve for PLLA, PL-MCD50, 67 and 83 at a) 100 °C, b) 60˚C and c) 25 °C.

stress at 25 °C is the highest for all the temperatures observed.

This behavior is typical for brittle plastics, indicating that the Tg

of the amorphous phase is higher than 25 °C.

At 60 °C, PLLA fractured at less than 100% strain, which is

much larger than at 25 °C in Figure 4b. For PL-MCD50 and 67,

similar behavior to PLLA was observed. These samples exhib-

ited yield points, followed by extensive elongation at an almost

constant strain, which is typical for a tough plastic where the

semicrystalline polymer shows an amorphous phase above Tg.

In contrast, PL-MCD83 was drawn to a maximum strain of

greater than 1000% and did not exhibit a yield point. The stress

is low at short elongation and increases with elongation, which

is typical for elastomers. Therefore, the mechanical properties

of these samples are governed by rubber elasticity. In other

words, MeCD prevents PLLA crystallization and lowers the Tg

for PL-MCD83. In fact, the Tg of PL-MCD83 is lowest among

the samples studied. This behavior is in accord with the TGA

and DSC results.

At 100 °C, the stress-strain curves did not exhibit yield points

except for PLLA in Figure 4a, since it contains a crystalline

phase. The other samples behave as elastomers; the largest

break strains are lower than those at 60 °C. This indicates that

the mobility of PLLA molecules is high at 100 °C and that the

tensile stress cannot propagate properly.

In addition, dynamic mechanical analysis (DMA) measure-

ments were conducted. Figure 5 shows the temperature depend-

ence tanδ. The peak assigned to the Tg for PLLA is approxi-

mately 70 °C [50]. For PL-MCD83 and 67, it is approximately

60 °C. Thus, it can be concluded that MeCD addition lowered

the Tg’s.

DSC-Raman measurementsThe Raman spectra of PLLA, PL-MCD50, 67, 83, and MeCD at

25 °C are displayed in Figure 6. The peak assignments of PLLA

are summarized in Table 1. MeCD exhibited scattering peaks at

1457, 1157, 1080, 857, and 449 cm−1. High-intensity character-

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Figure 5: Temperature dependence of tanδ for PLLA, PL-MCD50,PL-MCD67 and PL-MCD83.

Figure 6: Raman spectra for PLLA, PL-MCD83, 67, 50 and MeCD atroom temperature.

istic peaks for PLLA are at 2955 cm−1 (νCH), 1760 cm−1

(νC=O), 1452 cm−1 (δCH3), 1292 cm−1 (δCH), and 873 cm−1

(νC-Cα) [51,52]. Peaks at 857 and 449 cm−1 are characteristic

for MeCD [53].

In the Raman spectra of PL-MCD50, 67, and 83, the PLLA

peaks are clearly observed, while MeCD peaks are obscured.

This is caused by peak overlap and weak MeCD peak intensity

owing to the lower molar ratio of MeCD. Since the character-

istic peak at 857 cm−1 for MeCD overlapped with the peak at

873 cm−1, it is difficult to analyze the structure of MeCD

Table 1: Peak assignment of PLLA.

Peak assignment Wave number [cm−1]

νCH3 as 2998νCH,νCH3 S 2945, 2900νC=O 1762δCH3 as 1452δCH3 s,δCH 1385, 1365, 1292γCH 1215, 1180γCH3 1129, 1091νCα-Cβ 1042νCEster-Cα,νC-Cα 920, 872γC=O 735, 707τC-OE, δO=COE 510, 408, 394, 340δCC=O, γCCC 305, 237

through this peak. Although the other characteristic peak of

MeCD at 449 cm−1 is not typically employed, its intensity can

be used to measure the state of MeCD, since PLLA does not ex-

hibit a peak in this region.

The peak at 1760 cm−1 for PLLA shifts to a higher wavenumber

by approximately 6 cm−1 because of MeCD addition. This peak

shift is likely caused by the interaction between PLLA and

MeCD. Compared to the amorphous phase, the wavenumber of

the Raman peak for the crystalline phase is lower by 6 cm−1

[54]. Therefore, the addition of MeCD induces the amorphous

phase of PLLA. The shift of the peak at 1760 cm−1 indicates the

change in crystallinity. For other peaks, a peak shift was

insignificant. Although MeCD is mixed with PLLA, the IC was

seemingly not formed. As in the tensile drawing test,

PL-MCD83 exhibited the largest strain. Its structure was

investigated through DSC-Raman measurements.

Figure 7 shows the Raman spectrum of PL-MCD83 at a

temperature close to its Tg, Tc, and Tm. The peak intensities at

1760 and 873 cm−1, which are the characteristic peaks of

PLLA, decreased as the temperature increased. In addition, both

peaks broadened with temperature, which is remarkable above

Tc. Peak broadening and decrease in the peak intensity were

also observed for other peaks.

The peak position, intensity, and width provide important struc-

tural information. Figure 8 shows the stacked line profiles of the

Raman spectra of PL-MCD83 for the characteristic peak of

PLLA at 873 cm−1. The horizontal dotted line represents the top

of the peak at 873 cm−1. In this figure, the white region indi-

cates high intensity. Therefore, the vertical width of the white

region corresponds to the peak width. As the temperature

increases from room temperature to 60 °C, the peak width either

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Figure 7: Temperature dependence of Raman spectrum of PL-MCD83.

Figure 8: Stacked line profiles of Raman spectra of PL-MCD83 for the characteristic peak of PLLA at 873 cm−1.

remains nearly constant or slightly decreases. Above the Tg, the

peak width increases and reaches a maximum at 80 °C.

Between the Tg and 80 °C, the activation of segmental motion

induces local structural distribution. In this temperature range,

PLLA is in the amorphous state, and the molecular mobility is

suitable to be drawn. Therefore, the largest strain was obtained

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for PL-MCD83 in this temperature range. Above 80 °C, the

peak width begins to decrease, passes the minimum at approxi-

mately 100 °C, and then increases again. This sample under-

goes cold crystallization at approximately 100 °C, causing peak

narrowing at above 80 °C. The produced crystalline phase

prevents drawing above Tc, where the peak width monotoni-

cally increases. The peak broadening indicates that the local

structure of the sample is disturbed by the thermal energy. Thus,

in addition to the thermal properties, the local structural

distribution can also be deduced from the DSC-Raman

measurements. Furthermore, the tensile drawing behavior can

be explained through molecular mobility and local structural

distribution.

Transition analysis by continuous intensitychange of Raman spectrumSince the peak area is proportional to the width and intensity,

the peak intensity is also a good indicator for the local structure.

Principle components analysis (PCA) is one of the most well-

known techniques for analyzing intensity change in continuous

data [55,56]. DSC-Raman results can be divided into elements

of time, temperature, Raman scattering, and heat flow [57,58].

Since there was a one-to-one correspondence between the time

and temperature in DSC-Raman, parameters extracted from

temperature or time and intensities of scattering can be applied

to transition analysis. This method has the advantage of being

able to analyze the precise temperature dependence of each

peak, and by extension, each functional group.

Figure 9 shows the PCA results for PLLA from simple integra-

tion of its characteristic peaks. The peak intensity at 2955 cm−1

is nearly constant from room temperature to 70 °C. Above

70 °C, the intensity decreases suddenly. This decrease corre-

sponds with the Tg. In the DSC curve, the Tg of PLLA appeared

as a slight baseline change because this sample was not amor-

phous. In Figure 9, the intensity change at Tg is clear for PLLA.

Therefore, PCA analysis of DSC-Raman measurements can

detect thermal changes with high sensitivity.

The peak intensity decreases between 70 and 120 °C. Above

120 °C, the intensity increases slightly, which corresponds to

cold crystallization. Thus, the behavior of the peak intensity is

similar to the DSC heat flow. The intensity change of other

peaks is similar to that of the peak at 2955 cm−1.

Figure 10 shows the temperature dependence of the peak

intensities for PL-MCD83. The peak intensities decreased

clearly at approximately 60 °C, which corresponds to the Tg.

The Tg of this sample is lower than that of PLLA, which is in

accord with the deterioration of the crystalline phase from

MeCD addition.

Figure 9: PCA results of PLLA at 2955 cm−1, 1760 cm−1, 1452 cm−1,1385 cm−1, 1292 cm−1, 1129 cm−1, 873 cm−1, 736 cm−1 and449 cm−1.

Figure 10: PCA results of PL-MCD83 at 2955 cm−1, 1768 cm−1,1452 cm−1, 1385 cm−1, 1294 cm−1, 1128 cm−1, 873 cm−1, 736 cm−1

and 449 cm−1.

The peaks at 1385 and 1452 cm−1 increase at approximately

100 °C. The DSC data clearly indicate that cold crystallization

occurred at this temperature. Thus, the increase in the peak in-

tensities at 100 °C corresponds to cold crystallization. This

temperature was lower than that for PLLA. These results, along

with DSC-Raman measurements, indicate that MeCD addition

lowers the Tg and Tc.

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The change in peak intensity at 449 cm−1 was similar to those

of PLLA peaks. Since MeCD is the main contributor to this

peak, this behavior might be affected by the structure of MeCD.

At Tg, this peak also decreased, which indicates that the

mobility of MeCD increased with the segmental motion of

PLLA. Above Tg, the peak intensity at 449 cm−1 monotonically

decreases. The temperature dependence of this peak is similar to

that of PLLA over the temperature range observed. Therefore,

MeCD has good affinity for PLLA over a wide range of

temperatures. Thus, the analysis of DSC-Raman spectra reveals

not only the thermal behavior but also the local structural infor-

mation of each component with high sensitivity.

ConclusionThe effect of MeCD addition to PLLA on its physical prop-

erties was examined. As revealed through TGA and DSC, the

addition of MeCD lowers the Tg, Tc, and Tm. These results indi-

cate that MeCD prevents PLLA crystallization and increases the

amorphous content while enhancing molecular mobility in the

amorphous phase. This fact was reflected in the tensile drawing

results, in which PL-MCD83 exhibited the largest strain at

60 °C. Since the affinity of MeCD for PLLA is high, MeCD

may potentially be used as a plasticizer for PLLA. DSC-Raman

measurements showed results similar to those of TGA, DSC,

tensile drawing, and DMA. In addition, the detailed behaviors

of PLLA and MeCD during heating were observed. DSC-

Raman offers detailed information regarding the thermal behav-

ior and local structure simultaneously, and is useful for precise

temperature-dependent local structure analysis.

ExperimentalMaterialsMeCD was purchased from Wako Pure Chemical Ind. (Japan)

and used as received. In this MeCD, two methoxy groups per

glucopyranose unit were introduced in β-CD. PLLA (LACEA,

Mitsui Chemicals Inc.; Mn = 1.3 × 105, Mw = 2.6 × 105) was

used after removing the oligomer and polymerization catalyst

by dissolution in chloroform and precipitation in methanol. The

precipitated PLLA was dried at 100 °C for 24 h in vacuo prior

to film preparation. Chloroform and methanol were purchased

from Wako Pure Chemical Ind. (Japan) and used as received.

Sample film preparationSample solutions of 1 wt % PLLA and MeCD were prepared

separately by dissolving the requisite amounts of PLLA and

MeCD in chloroform at room temperature. The solutions were

mixed and vigorously stirred for 24 h. The PLLA/MeCD chlo-

roform solutions were cast onto a Petri dish and covered with an

aluminum foil with holes to allow solvent evaporation at room

temperature. The neat PLLA film was prepared with same way.

The obtained films were dried in vacuo. Casted films with

MeCD/PLLA ratios of 1:1 (50 wt % PLLA), 1:2 (67 wt %

PLLA), and 1:5 (83 wt % PLLA) were prepared. The samples

were abbreviated as PL-MCD and the wt % values of PLLA

were written after the abbreviated name (e.g., PL-MCD50 for

MeCD/PLLA = 1:1). The obtained films were used for the

experiments; for MeCD, the as received powder was used.

Thermogravimetry/differential thermalanalysis (TG-DTA)TG-DTA (Perkin-Elmer STA6000) was carried out at

10 °C min−1 under a nitrogen flow of 60 mL min−1 with 5 mg

samples placed in an open Al2O3 pan. For the stability test and

accuracy of complex mass ratio, the measurements were carried

out from 25 to 800 °C. MeCD was used as received.

Tensile drawing testTensile drawing of samples was carried out at 25, 60, and

100 °C using a Tensilon RTC-1325A tensile tester (A&D,

Japan). The initial sample length was 10 mm. Tensile drawing

measurements were carried out at a cross-head speed of

20 mm min−1.

Dynamic mechanical analysis (DMA)DMA was conducted from 25 to 140 °C at 10 °C min−1 at a

frequency of 1 Hz under a nitrogen atmosphere using

DMA861e (Mettler, Toledo). Samples were cut into 25.0 mm ×

3.0 mm films.

Constant rate DSC measurementsFor thermal behavior analysis, the constant rate DSC measure-

ments were carried out using a power compensation DSC

(Perkin-Elmer DSC 8500). Samples (2 mg) were packed in an

Al pan and the measurements were carried out at 10 °C min−1

under a nitrogen flow of 20 mL min−1. MeCD was used as

received.

DSC-Raman measurementsA power compensation DSC (Perkin-Elmer DSC 8500)

connected to a Raman spectrometer (Perkin-Elmer Raman

Station 400) through a DSC-Raman interface probe was used.

The laser irradiation of the samples and scattering collection

from the samples were conducted through glass fibers to mini-

mize the laser irradiation area and to avoid temperature

changes. Laser irradiation was configured to 100 mW for 4 s

with a heat flow amplitude of less than 8 mW or 0.03 °C [59].

The collection of Raman spectral data ranged from 3200 to

200 cm−1. DSC-Raman measurements were carried out from 25

to 190 °C at a heating rate of 2 °C min−1. The samples (4 mg)

were placed in an Al pan, and a SiO2 disk was placed on the

sample to minimize the effect of sample thickness on Raman

intensity. MeCD was used as received.

Beilstein J. Org. Chem. 2014, 10, 2997–3006.

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References1. Ikada, Y.; Jamshidi, K.; Tsuji, H.; Hyon, S.-H. Macromolecules 1987,

20, 904. doi:10.1021/ma00170a0342. Tsuji, H.; Hyon, S.-H.; Ikada, Y. Macromolecules 1991, 24, 5651.

doi:10.1021/ma00020a0263. Tsuji, H.; Hyon, S.-H.; Ikada, Y. Macromolecules 1991, 24, 5657.

doi:10.1021/ma00020a0274. Tsuji, H.; Ikada, Y. Macromolecules 1993, 26, 6918.

doi:10.1021/ma00077a0325. Tsuji, H.; Ikada, Y. Polymer 1999, 40, 6699.

doi:10.1016/S0032-3861(99)00004-X6. Tsuji, H.; Ikada, Y.; Hyon, S.-H.; Kimura, Y.; Kitao, T.

J. Appl. Polym. Sci. 1994, 51, 337. doi:10.1002/app.1994.0705102167. Takasaki, M.; Ito, H.; Kikutani, T. J. Macromol. Sci., Part B: Phys. 2003,

42, 403.8. Furuhashi, Y.; Kimura, Y.; Yoshie, N.; Yamane, H. Polymer 2006, 47,

5965. doi:10.1016/j.polymer.2006.06.0019. Tsuji, H.; Nakano, M.; Hashimoto, M.; Takashima, K.; Katsura, S.;

Mizuno, A. Biomacromolecules 2006, 7, 3316. doi:10.1021/bm060786e10. Ishii, D.; Ying, T. H.; Mahara, A.; Murakami, A.; Yamaoka, T.;

Lee, W.-k.; Iwata, T. Biomacromolecules 2009, 10, 237.doi:10.1021/bm8009363

11. Sawai, D.; Tamada, M.; Yokoyama, T.; Kanamoto, T.; Hyon, S.-H.;Moon, S. Sen’I Gakkaishi 2007, 63, 1. doi:10.2115/fiber.63.1

12. Sawai, D.; Tamada, M.; Kanamoto, T. Polym. J. 2007, 39, 953.doi:10.1295/polymj.PJ2007038

13. Zhang, J.; Tashiro, K.; Tsuji, H.; Domb, A. J. Macromolecules 2007, 40,1049. doi:10.1021/ma061693s

14. Kakiage, M.; Ichikawa, T.; Yamanobe, T.; Uehara, H.; Sawai, D.ACS Appl. Mater. Interfaces 2010, 2, 633. doi:10.1021/am900896q

15. Uehara, H.; Karaki, Y.; Wada, S.; Yamanobe, T.ACS Appl. Mater. Interfaces 2010, 2, 2707. doi:10.1021/am1005755

16. Yokoyama, Y.; Uehara, H.; Yamanobe, T. Key Eng. Mater. 2013, 543,71–75. doi:10.4028/www.scientific.net/KEM.534.71

17. Uehara, H.; Nakae, M.; Kanamoto, T.; Zachariades, A. E.; Porter, R. S.Macromolecules 1999, 32, 2761. doi:10.1021/ma981491z

18. Nakae, M.; Uehara, H.; Kanamoto, T.; Ohama, T.; Porter, R. S.J. Polym. Sci., Part B: Polym. Phys. 1999, 37, 1921.doi:10.1002/(SICI)1099-0488(19990801)37:15<1921::AID-POLB16>3.0.CO;2-M

19. Nakae, M.; Uehara, H.; Kanamoto, T.; Zachariades, A. E.; Porter, R. S.Macromolecules 2000, 33, 2632. doi:10.1021/ma991330a

20. Uehara, H.; Kakiage, N.; Yamanobe, T.; Komoto, T.; Murakami, S.Macromol. Rapid Commun. 2006, 27, 966.doi:10.1002/marc.200600199

21. Kakiage, M.; Yamanobe, T.; Komoto, T.; Murakami, S.; Uehara, H.J. Polym. Sci., Part B: Polym. Phys. 2006, 44, 2455.doi:10.1002/polb.20883

22. Kakiage, M.; Yamanobe, T.; Komoto, T.; Murakami, S.; Uehara, H.Polymer 2006, 47, 8053. doi:10.1016/j.polymer.2006.07.073

23. Uehara, H.; Yoshida, R.; Kakiage, M.; Yamanobe, T.; Komoto, T.Ind. Eng. Chem. Res. 2006, 45, 7801. doi:10.1021/ie060821y

24. Kakiage, M.; Sekiya, M.; Yamanobe, T.; Komoto, T.; Sasaki, S.;Murakami, S.; Uehara, H. Polymer 2007, 48, 7385.doi:10.1016/j.polymer.2007.10.018

25. Morioka, T.; Kakiage, M.; Yamanobe, T.; Komoto, T.; Higuchi, Y.;Kamiya, H.; Arai, K.; Murakami, S.; Uehara, H. Macromolecules 2007,40, 9413. doi:10.1021/ma071898g

26. Kakiage, M.; Sekiya, M.; Yamanobe, T.; Komoto, T.; Sasaki, S.;Murakami, S.; Uehara, H. J. Phys. Chem. B 2008, 112, 5311.doi:10.1021/jp709782g

27. Kakiage, M.; Uehara, H.; Yamanobe, T. Macromol. Rapid Commun.2008, 29, 1571. doi:10.1002/marc.200800316

28. He, Y.; Inoue, Y. Biomacromolecules 2003, 4, 1865–1867.doi:10.1021/bm034260v

29. He, Y.; Inoue, Y. J. Polym. Sci., Part B: Polym. Phys. 2004, 42, 3461.doi:10.1002/polb.20213

30. Dong, T.; He, Y.; Zhu, B.; Shin, K.-M.; Inoue, Y. Macromolecules 2005,38, 7736. doi:10.1021/ma050826r

31. Dong, T.; Shin, K.-m.; Zhu, B.; Inoue, Y. Macromolecules 2006, 39,2427. doi:10.1021/ma052687j

32. Shin, K.-M.; Dong, T.; He, Y.; Inoue, Y.J. Polym. Sci., Part B: Polym. Phys. 2005, 43, 1433.doi:10.1002/polb.20449

33. Joijode, A. S. Behavior and Properties of Self-Nucleated Poly (ethyleneterephthalate) (PET). MS Thesis, North Carolina State University, USA.2011, p. 41.

34. Shuai, X.; Wei, M.; Porbeni, F. E.; Bullions, T. A.; Tonelli, A. E.Biomacromolecules 2002, 3, 201. doi:10.1021/bm015609m

35. Ohya, Y.; Takamido, S.; Nagahama, K.; Ouchi, T.; Ooya, T.;Katoono, R.; Yui, N. Macromolecules 2007, 40, 6441.doi:10.1021/ma071198b

36. Xie, D. M.; Yang, K. S.; Xun, W. X. Curr. Appl. Phys. 2007, 7(Suppl. 1), e15. doi:10.1016/j.cap.2006.11.006

37. Mano, J. F. Macromol. Rapid Commun. 2008, 59, 1341.doi:10.1002/marc.200800180

38. Suzuki, T.; Morikawa, J.; Hashimoto, T.; Buividas, R.; Gervinskas, G.;Paipulas, D.; Malinauskas, M.; Mizeikis, V.; Juodkazis, S. Proc. SPIE2012, 8249. doi:10.1117/12.907028

39. Suzuki, T.; Takahashi, K.; Uehara, H.; Yamanobe, T.J. Therm. Anal. Calorim. 2013, 113, 1543.doi:10.1007/s10973-013-3098-z

40. Hoidy, W. H.; Ahmad, M. B.; Jaffar Al-Mulla, E. A.; Ibrahim, N. A. B.J. Appl. Sci. 2010, 10, 97. doi:10.3923/jas.2010.97.106

41. Aree, T.; Saenger, W.; Leibnitz, P.; Hoier, H. Carbohydr. Res. 1999,315, 199. doi:10.1016/S0008-6215(99)00033-6

42. Giordano, F.; Novak, C.; Moyano, J. R. Thermochim. Acta 2001, 380,123. doi:10.1016/S0040-6031(01)00665-7

43. Ren, Z.; Dong, L.; Yang, Y. J. Appl. Polym. Sci. 2006, 101, 1583.doi:10.1002/app.23549

44. Ljungberg, N.; Wesslén, B. J. Appl. Polym. Sci. 2002, 86, 1227.doi:10.1002/app.11077

45. Labrecque, L. V.; Kumar, R. A.; Davé, V.; MeCarthy, S. P.J. Appl. Polym. Sci. 1997, 66, 1507.doi:10.1002/(SICI)1097-4628(19971121)66:8<1507::AID-APP11>3.0.CO;2-0

46. Ljungberg, N.; Andersson, T.; Wesslén, B. J. Appl. Polym. Sci. 2003,88, 3239. doi:10.1002/app.12106

47. Mano, J. F.; Gómez Ribelles, J. L.; Alves, N. M.;Salmerón Sanchez, M. Polymer 2005, 46, 8258.doi:10.1016/j.polymer.2005.06.096

48. Turner, J. F., II; Riga, A.; O’Connor, A.; Zhang, J.; Collis, J.J. Therm. Anal. Calorim. 2004, 75, 257.doi:10.1023/B:JTAN.0000017347.08469.b1

49. Cao, X.; Mohamed, A.; Gordon, S. H.; Willett, J. L.; Sessa, D. J.Thermochim. Acta 2003, 406, 115.doi:10.1016/S0040-6031(03)00252-1

Beilstein J. Org. Chem. 2014, 10, 2997–3006.

3006

50. Nazhat, S. N.; Kellomäki, M.; Törmälä, P.; Tanner, K. E.; Bonfield, W.J. Biomed. Mater. Res. 2001, 58, 335. doi:10.1002/jbm.1026

51. Tan, H. Y.; Widjaja, E.; Boey, F.; Loo, S. C. J.J. Biomed. Mater. Res., Part B 2009, 91, 433. doi:10.1002/jbm.b.31419

52. Radjabian, M.; Kish, M. H.; Mohammadi, N. J. Appl. Polym. Sci. 2010,117, 1516. doi:10.1002/app.32046

53. Bertoluzza, A.; Rossi, M.; Taddei, P.; Redenti, E.; Zanol, M.;Ventura, P. J. Mol. Struct. 1999, 480–481, 535–539.doi:10.1016/S0022-2860(98)00734-0

54. Kister, G.; Cassanas, G.; Vert, M. Polymer 1998, 39, 267.doi:10.1016/S0032-3861(97)00229-2

55. Liem, H.; Cabanillas-Gonzalez, J.; Etchegoin, P.; Bradley, D. D. C.J. Phys.: Condens. Matter 2004, 16, 721.

56. Deerwester, S.; Dumais, S. T.; Landauer, T. K.; Furnas, G. W.;Harshman, R. J. Am. Soc. Inf. Sci. 1990, 41, 391.doi:10.1002/(SICI)1097-4571(199009)41:6<391::AID-ASI1>3.0.CO;2-9

57. Aach, J.; Church, G. M. Bioinformatics 2001, 17, 495.doi:10.1093/bioinformatics/17.6.495

58. Yasuniwa, M.; Iura, K.; Dan, Y. Polymer 2007, 48, 5398.doi:10.1016/j.polymer.2007.07.012

59. Hart, T. R.; Aggarwal, R. L.; Lax, B. Phys. Rev. B 1970, 1, 638.doi:10.1103/PhysRevB.1.638

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